It is well known that cellulose-containing fabrics, such as those made of cotton, linen, or regenerated cellulose or blends thereof, suffer from a disadvantage in that they wrinkle on washing and drying or during wear. Over the past several decades many procedures were developed in efforts to remedy this defect. These efforts resulted in processes using hundreds of different types of chemicals to treat the cellulose fabrics in order to create what has become known as "wash-and-wear" and, more recently, as "durable press" materials. At the present time, most of these processes involve a crosslinking reaction between adjacent cellulose molecules. This is, in general, accomplished by the use of reagents which cause the reaction between free hydroxyl groups in the repeating anhydroglucose groups in the cellulose unit through covalent linkages. Among these reagents are polyfunctional compounds which react with the hydroxyl groups to form bridges between adjacent cellulose molecules. Illustrative of such cross-linking agents are formaldehyde or formaldehyde liberating agents, and N-methylol compounds such as dimethylol urea, tetramethylol acetylene diurea, 1,3-dimethylol-4,5-dihydroxy ethylene urea, dimethylol ethylene urea, methylol triazones, melamine formaldehyde, and the like.
The crosslinks produced by these materials permit a certain amount of slipping between the cellulose molecules under stress but tend to return them substantially to their initial relationships when the outside stresses are removed. Thus, by introducing these crosslinkages into a cellulose fabric, a durable press is obtained. However, although some of these processes produce satisfactory commercial articles, the crosslinking process results in an attendant loss of tensile strength and abrasion resistance. Thus, durable press garments produced from such treated fabrics have a tendency to wear and fray particularly at the edges, such as the cuffs, collar lines and collar tips which are most exposed to friction in the course of being worn or in the course of mechanical laundering and drying.
Of the crosslinking agents mentioned above, formaldehyde is particularly attractive for a variety of reasons, especially where the durable press treatment is to be applied to completed garments. For this reason, many efforts have been directed to develop durable press processes in which vaporized formaldehyde can be used as the crosslinking agent. Among those recently developed for commercial use is one disclosed in U.S. Pat. No. 3,706,526 (Swidler et al). According to this process, cellulosic materials are exposed to hot vapors of formaldehyde and sulfur dioxide in the presence of moisture and cured to improve their dimensional stability, wrinkle resistance, crease retention, and smooth drying characteristics. This process is particularly advantageous for treating fabricated garments, such as knit or woven shirts, blouses, or trousers, to impart durable press properties thereto. Another important result of the Swidler et al process is that it significantly reduces shrinkage; more so, in fact, than the durable press "resin finishes". However, like other kinds of durable press garments, the garments so treated suffer from the tendency of the edges of cuffs or collar tips or other edge portions to fray much sooner than the rest of the fabric.
Many attempts have been made to remedy this type of defect. Thus, for example, U.S. Pat. No. 3,264,054 (Reinhardt et al) discloses a procedure whereby a softener for the material is applied to the fabric. According to this process, an aqueous emulsion of finely divided polyethylene resin is applied uniformly to a cotton material prior to treatment with gaseous formaldehyde and hydrogen chloride. This was found to result in a higher tearing strength and a higher wet and dry crease recovery angle than a cotton fabric similarly treated with formaldehyde without prior application of the polyethylene softener. However, this process suffers from the defect that it results in a product having poor resistance to laundering, while not overcoming the fabric-weakening effect of the hydrogen chloride.
Since the majority of the known durable press treatments require the presence of a catalyst and a relatively high treating temperature to cause the desired crosslinking reaction to proceed to the required extent, another attempted approach has been to control the degree of contact of the catalyst with the fabric. The durable press finish in the conventional processes for producing wrinkle resistant fabrics penetrates the entire fabric, causing crosslinking of the cellulose molecules substantially throughout the fibrous structure when the treated fabric is cured. Since the reduced abrasion resistance as compared with uncured cotton fabrics is due largely to crosslinked cellulose in the fibers located at the fabric surface, one process for remedying this defect, according to U.S. Pat. No. 3,402,988 (Reeves et al), has been to apply a catalyst deactivator to the surface of a fabric which had been impregnated with a crosslinking agent, but prior to the curing of the latter. Although this process is in general successful in improving the abrasion resistance of the durable press fabrics, it is difficult to apply without seriously impairing the desired durable press effect and is applicable only to those processes where the crosslinking agent can be applied to the fabric mixed with the required catalyst and then dried prior to the finishing step. Thus, it must be possible to interpose a step of applying a catalyst deactivator to the fabric surface between the drying step and the high temperature curing step. For this reason, it is effectively applicable only to those systems using, for example, a solid catalyst such as zinc chloride or other non-volatile salt and a nonvolatile crosslinking agent such as dimethylol urea, dimethylol ethylene urea, and the like, which can be applied in aqueous solutions or emulsions.
Another proposed method for improving the abrasion resistance of durable press fabrics is that disclosed in U.S. Pat. No. 3,457,024 (Chipalkatti et al) in which the cellulose-containing textile material is first reacted with an ester of 1,3-dihalopropanol-2 or 1,2-dihalopropanol-3 prior to treatment with the crosslinking agent. The reaction of the ester with the cellulosic textile material is carried out in the presence of an 18-20 percent aqueous sodium hydroxide solution in the slack condition, and the thus reacted cellulosic textile is then washed free of alkali and further reacted with a finishing agent, with or without prior drying. During the washingoff of the alkali, or during any of the subsequent operations, the cellulosic textile material must be stretched nearly to its original dimensions. Although this procedure will improve the abrasion resistance of the fabric, it requires a number of additional steps and additional equipment which cause complications and increase the cost of the finished product.
Still another proposed process for improving the abrasion resistance of crosslinked cellulose products is disclosed in U.S. Pat. No. 3,528,762 (Lauchenauer). According to this process, the crosslinking agent and the catalyst are applied first to the fabric. The latter is then subjected to an atmosphere containing a catalyst poison. This produces a fabric in which the cellulose fibers at the surface are crosslinked to a lesser degree than the fibers in the interior of the fabric. Here again, the crosslinking agent and catalyst must be such that they can be applied to the fabric without curing so that the fabric containing them may be cured while being subjected to the atmosphere in which a catalyst poison is present.
Still another proposed method for improving the abrasion resistance of fabrics particularly on the creases of trouser cuffs, has been to apply a permanent wear-resistant edge coating which has greater abrasion resistance than the fabric of which the cuffs are made. Such a process is disclosed in U.S. Pat. No. 3,166,765 (Getchell).